<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>my css3</title>
    <style>
        .c1 {
            display: block;
            width: 300px;
            height: 300px;
            background-color: lightgray;
        }
    </style>
</head>
<body>
<span class="c1">
    达内云计算 cloud computing
</span>
</body>
</html>